This invention generally relates to prevention of illegal duplication of digital data, and more particularly to a data reproduction apparatus, a data recording apparatus, a circuit element, a data reproduction method and a data recording method wherein digital watermark status is utilized to prevent illegal duplication of digital data.
On a recording medium such as a DVD (Digital Versatile Disc), a large amount of data, for example, for one movie, can be recorded as digital information. As it becomes possible to record image information and so forth as digital information in this manner, it progressively becomes significant to prevent illegal duplication to achieve protection of the copyright holder.
For example, for the DVD-Video, a copyright protection technique called CSS (Content Scramble System) is available. Where the CSS is applied, although a DVD-Video file can be copied onto a hard disk, since MPEG (Moving Picture Experts Group) data of the copied file is in an encrypted state, the data cannot be decoded by an MPEG decoder. Consequently, copy of the digital data can be prevented. In order to cancel the CSS, a predetermined encryption key is required.
Further, the CSS approves application thereof only to DVD-ROM (Digital Versatile Disc-Read Only Memory) media, and a CSS contract prohibits application to recordable DVD media such as the DVD-R, DVD-RW, DVD+R and DVD+RW. Accordingly, bit-by-bit copy from a DVD-Video disk to such recordable DVD media as mentioned above is not an action approved by the CSS contract.
This quite similarly applies to the CPPM (Content Protection for Pre-Recorded Media) which is a copyright protection technique for the DVD-Audio.
However, since such a situation that DeCSS software for decrypting the encryption of the CSS is distributed on the Internet has occurred, there is a problem that an action of decrypting the encryption of the DVD-Video into plain text and recording the plain text onto a recordable DVD can be executed simply.
In order to take a countermeasure against the action just described, a technique of utilizing a digital watermark technique to prevent illegal duplication has been proposed. The digital watermark technique embeds predetermined digital watermark status into image information and/or sound information in advance and detects, upon recording or reproduction, the digital watermark status to prevent illegal duplication.
Various disk drives have been proposed which detect digital watermark status to prevent illegal duplication. Such disk drives, however, have the following problems.
In particular, for example, it has been proposed in Japanese Patent Laid-Open No. 2000-115727 to detect digital watermark status by means of a DVD drive apparatus and control, if it is discriminated from the detected digital watermark status that the DVD has been duplicated illegally, to return an error status, which instructs not to permit any of readout and writing, to a personal computer (PC) which controls the DVD driver apparatus.
However, since a definition of an error status based on such detection of digital watermark status as described above is not applied between the personal computer and the DVD drive apparatus, the error status received from the drive apparatus is an error not expected by the personal computer. Consequently, it is estimated with a considerably high degree of possibility that the personal computer may suffer from malfunction of application software or an abnormal end and, in the worst case, the personal computer may be placed into a hang-up state.
Also a technique has been proposed that a DVD player or a DVD recorder detects digital watermark status recorded on a DVD, discriminates based on the detected digital watermark status whether or not the DVD is an illegal duplicate, and restricts its output if the DVD is an illegal duplicate. However, such a DVD player or a DVD recorder as described above is configured such that the output restriction is performed at a stage later than an MPEG decoder under the control of a CPU (Central Processing Unit). Therefore, there is a problem that production of an illegally duplicated DVD or reproduction of an illegally duplicated DVD can be executed simply by circuit reconstruction such as change of wiring lines or alteration to firmware.